Systems and methods for providing a system-on-a-substrate

ABSTRACT

This relates to systems and methods for providing a system-on-a-substrate. In some embodiments, the necessary components for an entire system (e.g., a processor, memory, accelerometers, I/O circuitry, or any other suitable components) can be fabricated on a single microchip in “bare die” form. The die can, for example, be coupled to suitable flash memory through a substrate and flexible printed circuit board (“flex”). In some embodiments, the flex can extend past the substrate, die, or both, to allow additional, relatively large components to be coupled to the flex. In some embodiments, the die can be coupled to the flash memory through the flex and without a substrate. In some embodiments, component test points can be placed on the flash memory side of the substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 61/154,101, filed on Feb. 20, 2009, which is herebyincorporated by reference herein in its entirety.

FIELD OF THE DISCLOSURE

This relates to systems and methods for providing asystem-on-a-substrate. In particular, this relates to systems andmethods for reducing the total size of a system's circuitry by providingall of the components of the system on the same microchip.

BACKGROUND OF THE DISCLOSURE

Systems, such as systems for an electronic device, are often createdfrom multiple components. For example, the components of a system caninclude one or more of a processor, memory (e.g., RAM, SDRAM, DDR RAM,or ROM), CODEC circuitry, Input/Output (“I/O”) circuitry, communicationcircuitry, accelerometers, capacitors, inductors, or any other suitablecomponents. Traditionally, each of these components are a distinct“entity” and can be created on a separate microchip or can be includedin a separate package.

To create the circuitry for the entire system, the separate components(e.g., separate microchips) are typically coupled together through aprinted circuit board (“PCB”) or other suitable medium. The PCB can befabricated with the appropriate wiring or routing to suitably connectall of the separate components.

SUMMARY OF THE DISCLOSURE

This relates to systems and methods for providing asystem-on-a-substrate. For example, rather than including the componentsof a system as discrete entities (e.g., as discrete microchips or asdiscrete parts), the components of a system can be formed together in“bare die” form. In other words, the components can be formed togetheron a single substrate, such as a silicon die or a die of other suitablematerial. In this manner, the components of an entire system can bedensely and efficiently packed together, thus allowing the system toachieve a smaller size than a system using components that are discreteentities.

The components can include, for example, one or more of a processor,memory (e.g., RAM, SDRAM, DDR RAM, ROM), CODEC circuitry, Input/Output(“I/O”) circuitry, communication circuitry, accelerometers, capacitors,or any other suitable components. A system utilizing these componentscan be included in any suitable electronic device such as, for example,a cellular telephone, a personal data assistant (“PDA”), a digital mediaplayer (e.g., an iPod™ available from Apple Inc. of Cupertino, Calif.),a computer, or any other suitable electronic device.

In some embodiments, a die including the components of a system can becoupled to a substrate. The substrate, in turn, can be coupled to aflexible printed circuit board (“flex”). The substrate and the flex caninclude any suitable wiring and routing to electrically couple the dieto other parts of the system such as, for example, a flash memory. Insome embodiments, the flex can be coupled to a different surface of thesubstrate than the die. In some embodiments, the flex can be coupled tothe same surface of the substrate as the die.

In some embodiments, the flex can include a ledge to which one or morecomponents can be coupled. In some embodiments, a system can be createdwhich does not include a substrate. In this case, all necessary wiringcan be provided through the flex. In some embodiments, test points canbe provided for a component of a die. For example, the test points canbe included in a portion of the flex located substantially below thecomponent to be tested.

In some embodiments, rather than being included together in a singledie, the components of a system can be included as discrete entities.The discrete entities can be coupled to a substrate rather than beingcoupled to a printed circuit board (“PCB”). As a substrate can have morestringent design rules than a PCB, coupling the discrete entities to thesubstrate can allow for a system that is smaller and more compact insize. For example, the wiring for the system can be created using lesslayers and can be formed more densely in a substrate than in a PCB.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other advantages of the invention will be apparent uponconsideration of the following detailed description, taken inconjunction with accompanying drawings, in which like referencecharacters refer to like parts throughout, and in which:

FIG. 1 is an illustrative printed circuit board system;

FIG. 2A is an illustrative system including multiple components mountedon a printed circuit board;

FIG. 2B is an illustrative system including multiple components mountedon a substrate in accordance with some embodiments of the invention;

FIG. 3 is an illustrative system-on-a-substrate in accordance with someembodiments of the invention;

FIG. 4 is an illustrative system-on-a-substrate including a ledge inaccordance with some embodiments of the invention;

FIGS. 5, 6, 7A, and 7B are illustrative systems-on-a-substrate inaccordance with some embodiments of the invention; and

FIG. 8 is an illustrative process for creating a system-on-a-substratein accordance with some embodiments of the invention.

DETAILED DESCRIPTION OF THE DISCLOSURE

Generally, a system can be made up of several different components. Asused herein, the term “component” can refer to any suitable part orconstituent of a system such as, for example, one or more of aprocessor, memory (e.g., RAM, SDRAM, DDR RAM, ROM), CODEC circuitry,Input/Output (“I/O”) circuitry, communication circuitry, accelerometers,capacitors, or any other suitable components. Each of these componentscan generally be fabricated on their own, distinct microchip orfabricated as a discrete and distinct “entity”. For example, theprocessor of a system may be on one microchip, the memory of the systemmay be on a different microchip, and a capacitor may be a separateentity from both the processor microchip and the memory microchip. Asused herein, the term “entity” can refer to a component when it isincluded in a system as a discrete, pre-packaged part or microchip.

In this manner, all of the system components can be discrete andgenerally pre-packaged entities. To create a system with an entire setof components, these separate entities can be coupled together through,for example, a printed circuit board (“PCB”) or other suitable medium. APCB can generally be a rigid board that is formed from one or moredielectric layers. The dielectric layers can be designed with contactsto electrically couple the PCB to the components (e.g., to the discretemicrochips) and designed with various conductive pathways toelectrically couple the various components to each other.

FIG. 1 shows an illustrative PCB 100 that can be used for couplingtogether the components of system 10, when the components are eachdiscrete entities. For example, discrete entities such as a processormicrochip 102, memory microchip 104, and one or more capacitors 106 canbe coupled together through PCB 100. PCB 100 can be formed withconductive pathways or wiring (e.g., wiring 108 or 110) that cansuitably provide electrical connections between the various entities ofsystem 10 to couple the entities together.

Although FIG. 1 illustrates a processor, memory, and capacitors, oneskilled in the art could appreciate that one or more of theabove-mentioned discrete entities (e.g., CODEC circuitry, I/O circuitry,communication circuitry, accelerometers, or any other suitablecomponents) could alternatively or additionally be illustrated inFIG. 1. As used herein, when a specific illustration of a component isprovided, one skilled in the art could appreciate that the specificillustration is given merely for illustration and not for limitation,and that any other suitable component (e.g., a processor, a memory,CODEC circuitry, I/O circuitry, communication circuitry, accelerometers,capacitors, or any other suitable component), could alternatively oradditionally have been illustrated.

As mentioned above, a PCB (e.g., such as PCB 100 of FIG. 1) cangenerally couple together the various components or entities for anentire system of an electronic device. For example, the PCB may coupletogether the necessary entities for a system used in a cellulartelephone, a personal data assistant (“PDA”), a digital media player(such as an iPod™ available from Apple Inc. of Cupertino, Calif.), acomputer, or any other suitable electronic device. Because thecomponents of the system are each formed as their own, discrete entitiesand are generally pre-packaged instances, the minimum size of the systemcan be significantly constrained by the discrete entities. As oneexample, the use of the discrete entities may cause difficulties inrouting the wiring between the entities, thus requiring additionalwiring and space to effectively couple the entities together. As anotherexample, because they are generally pre-packaged entities and cannot bealtered, the size of the entities may not be decreased. Theselimitations may, in turn, limit how small in size the electronic devicethat is utilizing the system can become.

FIG. 2A shows a side-view of a system 200 that can include componentsthat are each discrete entities (e.g., discrete microchips, discreteparts, or both). System 200 can include PCB 202 that can be used forcoupling together the discrete entities of system 200. For example, PCB202 can correspond to PCB 100 of FIG. 1. In some embodiments, ratherthan being placed side-by-side, the discrete entities of a system mayneed to be placed on top of one another. For example, FIG. 2A showsmemory microchip 204 that can be placed on processor microchip 206.Similar to FIG. 1, although a memory microchip and a processor microchipare illustrated in FIG. 2A, one skilled in the art could appreciate thatany other suitable components could alternatively or additionally havebeen illustrated.

Memory microchip 204 and processor microchip 206 can be coupled to oneanother and to PCB 202 through any suitable method. For example, theymay be coupled to one another through any suitable Surface MountTechnology, such as a Pin Grid Array (“PGA”), Land Grid Array (“LGA”),or Ball Grid Array (“BGA”). For example, solder balls such as one ormore solder balls 208 can be used to couple processor microchip 206 toPCB 202 and one or more solder balls 210 can be used to couple memorymicrochip 204 to processor microchip 206 through a Ball Grid Array.

In some embodiments, a flash memory or any other suitable memory mayalso be used by the system. For example, a flash memory such as a NANDgate based flash memory may be used. In this case, the NAND memory canalso be coupled to the PCB. For example, FIG. 2A illustrates memory 212that can be coupled to the bottom surface of PCB 202. Similar to thediscrete components (e.g., memory microchip 204 and processor microchip206), memory 212 can be coupled to PCB 202 through any suitable methodor Surface Mount Technology.

Due to the stacking of the discrete entities on top of each other (e.g.,such as memory microchip 204 stacked on top of processor microchip 206),the minimum size of the total circuitry of the system may additionallybe limited in the z-direction (i.e., in the height of the system) bythis stacking. Thus, the use of discrete entities (e.g., discretemicrochips) to create the system may limit the minimum size that thesystem can achieve in both the x-y direction (i.e., the surface area)and in the z-direction (i.e., the height). This may, in turn, once againlimit the minimum size that an electronic device utilizing the systemcan achieve.

In some embodiments, the discrete entities of a system (e.g., discretemicrochips, discrete parts, or both) can be coupled to a substraterather than being coupled to a PCB. For example, FIG. 2B shows system220 in which one or more entities 224 can be coupled to substrate 226.Each entity 224 can include any suitable discrete entity such as aprocessor, memory, CODEC circuitry, an accelerometer, a capacitor, aninductor, or any other suitable components or combination of componentsof system 220. Moreover, only one instance of entity 224 is illustratedin FIG. 2B for the purpose of simplicity. However, system 220 canalternatively include any other suitable number of instances of entity224. In some embodiments, memory 232 can be coupled to a surface ofsubstrate 226. Memory 232 can include, for example, a flash memory(e.g., a NAND gate based flash memory) or any other suitable memory.

Each entity 224 can be coupled to substrate 226 through any suitablemethod or Surface Mount Technology. By coupling the components of system220 to substrate 226 rather than to a PCB, the usage of a PCB in system220 can be limited or even eliminated. Limiting or eliminating the usageof a PCB in a system can beneficially reduce the size of that system.For example, a substrate may have more stringent design rules than aPCB, thus allowing the wiring through the substrate to be denser. This,in turn, can provide for a system in which distinct entities are mountedto a substrate to achieve a smaller size than a system in which thedistinct entities are mounted to a PCB. For example, a PCB may havedesign rules requiring traces that are at least 60 micrometers in widthand requiring at least 60 micrometers in between traces, while asubstrate may have design rules requiring traces that are at least 15micrometers in width and requiring at least 15 micrometers in betweentraces. Accordingly, in this scenario, a substrate can achieve wiringthat is 4 times denser than the wiring of a PCB. In some embodiments, bymounting discrete entities to a substrate, for example, a 4-layer,0.2-millimeter thick substrate can be used in place of a 6-layer,0.5-millimeter thick PCB.

In some embodiments, rather than using discrete, separate entities forthe various components of a system, the components of a system can beformed together in a single microchip. For example, if the components ofa system are a processor, memory, I/O circuitry, accelerometer, andvarious capacitors, all of these components can be formed together in“bare die” form (e.g., the components can be created on a singlesubstrate, such as a silicon die or a die of other suitable material).This can allow all of the components of the system to be integratedtightly together on one microchip, thus significantly reducing theachievable size of the total circuitry of the system. Thus, rather thanmultiple microchips on a PCB, the entire system can all be formed inbare die form on a single microchip. This “system-on-a-substrate” canresult in the same functionality for the system while greatly reducingthe system in size (e.g., the size can be reduced by 40-80%, by 50-70%,by 55-65%, or by 60%).

FIG. 3 shows an illustrative system-on-a-substrate 300.System-on-a-substrate 300 can include die 302. Die 302 can be fabricatedto include any or all of the components of an entire system, such as oneor more of components 304. For example, each component 304 can includeany of the necessary circuitry to form one or more processors, memory,CODEC circuitry, I/O circuitry, communication circuitry, accelerometers,capacitors, inductors, or any other suitable components. Although eachof components 304 are illustrated as separate blocks in FIG. 3, becausethe components are fabricated into the same die, in some embodimentscomponents 304 can overlap with or go through one another. For example,transistor gates, wiring, or both of one component can be fabricated inthe same transistor gates and wiring of another component. Accordingly,because each of components 304 can be fabricated on the same die 302,the components can be tightly integrated and densely formed, thussignificantly reducing the overall size of system 300.

In some embodiments, die 302 can be electrically coupled to substrate306. In some embodiments, there can be a flexible printed circuit board(“flex”) 310 coupled to the opposite side of substrate 306 as die 302.Flexible printed circuit boards can include multiple layers (e.g., ofwiring levels) and can be used, for example, to provide wiring andelectrical connections between one board to another board, one board toa microchip, or from one microchip to another microchip. Flexibleprinted circuit boards are generally lighter, thinner, and more ductilethan a PCB, and can be beneficial to use in systems having limitedspace. In some embodiments, flex can be used without a substrate tosupport a die.

Flex 310 can include multiple layers (e.g., two layers of wiring, threelayers of wiring, or any suitable number of layers of wiring). Flex 310and substrate 306 can be used to provide the necessary wiring androuting to connect entities 304 to one another and/or connect die 302 toany suitable type of memory, such as flash memory. For example,substrate 306 and flex 310 can connect die 302 to memory 312.

In some embodiments, flex 310 can include a ledge that extends beyondmemory 312, die 302, or both. In this case, rather than being fabricatedin die 302, one or more components can be coupled to this ledge. Forexample, FIG. 4 shows illustrative system-on-a-substrate 400 that caninclude ledge 414 in accordance with some embodiments. Similar tosystem-on-a-substrate 300, system-on-a-substrate 400 can include flex410 that can be coupled to substrate 406 and memory 412.

In some embodiments, at least one component 404 a can be coupled toledge 414. This design can be beneficial when, for example, component404 a is a relatively large component such as a large capacitor or otherlarge component. For example, if component 404 a is taller than theheight of die 402, by coupling component 404 a to ledge 414 instead ofincluding it within die 402 along with the other components (e.g.,components 404 b), the height of system-on-a-substrate 400 may besignificantly reduced. By reducing the height of system-on-a-substrate400, the size of an electronic device that utilizessystem-on-a-substrate 400 may also be significantly reduced. In someembodiments, rather than being vertically offset from flex layer 410, aledge such as ledge 416 may alternatively be aligned vertically withflex layer 410. Ledge 416 may, for example, couple to a component suchas component 404 c.

In some embodiments, rather than being on the opposite side of thesubstrate from the components, the memory (e.g., NAND memory, or anyother suitable memory) can alternatively or additionally be on the sameside of the substrate as the components. For example, FIG. 5 showssubstrate 506 that can have die 502 (e.g., including one or morecomponents 504) coupled to a single side of the substrate. Memory 512can also be coupled to the same side of substrate 506 (e.g., throughflex 510) as die 502. In some embodiments, die 502, memory 512, or both,may have portions of themselves coupled to each side of substrate 506(not shown).

In some embodiments, a system-on-a-substrate can be created without asubstrate layer. Instead, all of the necessary wiring and routing can bedone through a flexible printed circuit board. For example, FIG. 6 showssystem-on-a-substrate 600 that includes die 602 and memory 612 coupledtogether solely through flex 610. Die 602 can include one or moreentities 604 and memory 612 can be included on either or both sides offlex 610.

In some embodiments, component test points can be added to a system. Thecomponent test points may allow a person to perform tests on a microchipafter the microchip has been fabricated. For example, the test pointscan be used to perform failure analysis, performance analysis, or anyother suitable testing on the entire microchip or on portions of themicrochip.

FIG. 7A shows system 700 that can include one or more test points 722.In some embodiments, test points 722 can be positioned in a manner thatallows them to be used for testing one or more components (e.g.,components 704 and/or component 705) that can be fabricated in die 702.For example, test points 722 can be placed in positions near orunderneath component 705, (or any other suitable component, to allow fortesting of that component. In some embodiments, some or all of testpoints 722 can be placed on the side of substrate 706 that faces memory712. Placing test points on the memory side of a substrate, as opposedto placing test points adjacent to the component being tested (e.g.,component 705), can allow for testing of that component while causingless damage to the component. In this scenario, a portion of flex 710can be removed to form a gap in flex 710, and one or more test points722 can be included in that gap.

In some embodiments, to perform testing on component 704, component 704can be removed from system 700. For example, component 704 can beremoved by cutting through die 702 and around component 704 along lines730 and 732. Memory 712 can then be decoupled from flex 710. This canallow test points 722 to be easily accessed when performing testing ofthe component. For example, FIG. 7B shows portion 750 after component754 has been cut out and the memory has been decoupled, thus resultingin easily accessible test points 722. In this manner, test points 722can be exposed on a surface of portion 750 to allow, for example, a testprobe or other suitable testing device to come into contact with one ormore of test points 722.

FIG. 8 shows illustrative process 800 for creating asystem-on-a-substrate. At step 802, a die can be created that includessome or all of the various components of a system. The components caninclude, for example, a processor, memory, CODEC circuitry, Input/Output(“I/O”) circuitry, communication circuitry, accelerometers, capacitors,any other suitable components, or any combination of the above. As allof the components of the system can be created in the same die, in someembodiments the components can overlap with or go through one another.The die can include, for example, a silicon die or a die of any othersuitable material.

At step 804, the die can be coupled to a surface of a substrate. At step806, a surface of the substrate can be coupled to a flexible circuitboard (“flex”). The flex and the substrate may, for example, be used toprovide the wiring and routing to couple the die to any other suitableentities in the system. In some embodiments, as illustrated in FIG. 3,the die and the flex can be coupled to different surfaces of thesubstrate. In some embodiments, as illustrated in FIG. 5, the die andthe flex can be coupled to the same surface of the substrate.

At step 808, a surface of the flex can be coupled to a memory. In turn,the flex and the substrate can provide the necessary wiring and routingto electrically couple the memory to the die. The memory can include,for example, a flash memory (e.g., a NAND gate-based flash memory) orany other suitable memory.

At step 810, other suitable components can be coupled to a ledge of theflex. For example, the flex can include a ledge such as ledge 414 ofFIG. 4. A component can then be coupled to the ledge, such as component404 a or 404 c of FIG. 4. The ledge may be vertically offset from theflex or vertically aligned with the flex. The component can include, forexample, a component that is relatively large in comparison to the dieor in comparison to the system. In this manner, by coupling thecomponent to the ledge rather than including it in the die, a system canbe created that is potentially smaller in the z-direction (e.g., inheight).

The process discussed above is intended to be illustrative and notlimiting. Persons skilled in the art can appreciate that steps of theprocess discussed herein can be omitted, modified, combined, orrearranged, or that any combination of these steps or any additionalsteps can be performed without departing from the scope of theinvention. For example, in some embodiments, a substrate can beeliminated and a die can be coupled directly to the flex. In thisscenario, step 804 of process 800 can be omitted, and step 806 canmodified such that a surface of the die is coupled to the flex. Asanother example, in some embodiments step 810 can be omitted and asystem-on-a-substrate can be created that does not include componentscoupled to a ledge of the flex.

Various configurations described herein may be combined withoutdeparting from the invention. The above described embodiments of theinvention are presented for purposes of illustration and not oflimitation. The invention also can take many forms other than thoseexplicitly described herein. For example, in addition to or instead ofcoupling a flex to a memory (e.g., memory 312 of FIG. 3, memory 412 ofFIG. 4, memory 512 of FIG. 5, memory 612 of FIG. 6, or memory 712 ofFIG. 7), the flex can be coupled to a component (e.g., a component notincluded in a die). Accordingly, it is emphasized that the invention isnot limited to the explicitly disclosed methods, systems, andapparatuses, but is intended to include variations to and modificationsthereof which are within the spirit of this disclosure.

1. A method for creating a system, the method comprising: coupling amicrochip to a first surface of a substrate, wherein the microchipcomprises every system component of the system; coupling a secondsurface of the substrate to a flexible printed circuit board (“flex”);coupling at least one test point to at least one system component of themicrochip, wherein the test point is operable to indicate the quality ofthe at least one system component; and separating a first portion of thesystem from a remaining portion of the system, wherein the first portioncomprises the at least one test point and the at least one systemcomponent.
 2. The method of claim 1, further comprising coupling theflex to an entity, wherein the flex and the substrate electricallycouple the microchip to the entity.
 3. The method of claim 2, where theentity comprises a flash memory.
 4. The method of claim 1, wherein theat least one test point is positioned in the flex.
 5. The method ofclaim 1, wherein the first portion further comprises a memory componentcoupled to the at least one test point.
 6. The method of claim 5,further comprising decoupling the memory component from the at least onetest point, wherein the decoupling allows the at least one test point tobe accessed by a test probe.